Insulating Garage for a workshop

[Mattatooi]

I know there are a few threads on this but most appear to relate to full conversions to habitable living areas etc. My situation is a little different. I want to insulate garage for the purpose of a workshop (woodwork mainly);

I currently have a standard single brick garage that is approx 3.1m(W) x 6m(L) x 2.31m(H) internal dimensions, not including the 4 double brick pillars. It is flat roofed. The roof appears to be OSB with the felt stuff on top (don't know name). The floor is concrete. I cannot tell if it has a DPM. I doubt it. The garage itself is built on a sloping garden, so the back of the garage is quite high up compared to driveway point. There are 2 windows (1 at back wall, and 1 on side), up and over garage door. Currently no side door as previous owner blocked up, but will be easy enough to open up again.

I want to be able to use the garage as a workshop and not be freezing my balls off lol. I would also love it so that the garage was relativity not so damp! I have no idea on cost right now, so if anyone has a wide ranging ballpark figure of costs would be great.

Some questions;

Flooring

1) What is the best option for insulation, and which would be cheapest or less hassle? Reading around, looks like I would need to dig out floor... Maybe I have to with the limitation on height to celiling?

2) If I do dig out and insulate, is it easier to put floating floor or just get it filled again with concrete etc?

Walls

3) What wall thickness of insuatlion can I get away with to maximise size? As its not "habitable" I don't need to condone to house regs ??

4) I see you can get plasterboard with insulation attached. Any good or waste of money?

5) What would be efficent and cheap way to finish walls. Could I get away with OSB?

6) Garage door. I really have no idea how I go about insulating this? Do I need to look at a new door? Perhaps 2 hinges?

7) What about blocking up the garage door wall. Is this a bad idea? Can I even do this? Will this effect house re-sale value, or anything? Does this effect mortgage even? Not planning on moving anytime soon. Looking to stay for a very long time.

Celing

8) Guessing insulation between joists. Recommended product / thickness? I need to leave gap at top??

9) What about ventilation?

Other

10) Would it be cheaper and easier to install to just use conduit for all electrical cables etc for lighting and sockets?

11) Planning permission, from what I have read, I do not need any planning permission generally for this type of work, do I need to have building control involved??

12) Lastly, if you have any good websites/documents on this topic, please share!


Thats all I can think off for now. I probably have typed far too much and now most people will ignore this thread. Ahh, hope not.

Any comments are highly appreciated!

Thanks !

 

[theprinceofdarkness]

The problem is that at present the inside of the garage will be quite well ventilated (leaky door!) so any moisture migrating through the walls will disappear. Now when its converted into a workshop any water that migrates through the walls/roof/floor must be coped with. I think the first thing to door is to vent the ceiling void. Basically cut holes right up against the roof wood so when the void is sealed with your insulation, you can still get cross ventilation. If the roof has not got overhanging eaves then some form of protection will be need to stop rain blowing in to them. So a 1" diam hole in each wall in between each pair of joists. Then 4" of celotex and finish off with what ever plasterboard/hardboard/... Paint it white before you do anything else!
Floor just paint the floor with SBR/cement solution, it puts a leathery waterproof finish on the concrete. Now if the walls are battened and insulated, any water will dribble down and pool on this new DPC, so a way must be use to allow it to leak away and not pool over the floor.
Whoops wifes dragging me away, back later.
Frank

 

[Mattatooi]

Hi, thanks for reply. Teased me with information lol.

So regarding ceiling. Joists I think are 7" high. So are you saying drill holes in all the joists to allow air to vent across at 90' to the joist runs? How big are you talking? Do I need to effectively treat the ceiling as an upside down suspended floor but not actually suspended lol? So would some air vents on just below roof line work around the garage? Not sure how this would work with the guttering? Took a picture of ceiling area;



Also ive only noticed now that all the joists have got old nails in them. I think prev owner may have had some form of ceiling in but then removed it. Odd !

Flooring, sounds interesting. Maybe I do have this? I found an old pic on here from when I was adding storage to garage a while back.



Kind of shows the floor. Here is a close up i just took;



The white stuff is just dust / plasterboard dust etc. But its kind of painted and as you can see its not smooth or anything, all very rough like this. I acutally have loads of old carpet all down on the floor at the moment. My garage floor is pretty much level with my driveway. Reason I thought I would need to insulate was I had read that if I insulated ceiling and walls and not the floor, it could make the added insulation not as efffective as I would get alot heat loss through floor?

And you just touched on the walls, so hopefully you come back and answer more. But presumably when going down batton route, I would need a form of DPC barrier from wall to timber, so as the timber is not touching the brick? Much appreicated!

Am I crazy to try and attempt this myself or should I get some builders in and get some prices? I was hoping to keep costs down, but looking more into the research, there is a fair bit of work to do.

 

[theprinceofdarkness]

It looks as though you have a overhanging roof, so I would put vents in the soffit board, if you don't then vents in the facia board. The idea is to vent each volume between pairs of joists. Drill the joists for your lighting cable and install above the 4" celotex, which seems to be fixed with expanding foam (prop up or put up temporary battens under the joist until the foam has set). Then I would put up a VCL, very thin plastic sheeting, this stops any moisture from inside the garage condensing in the roof space, drape it 6"+ down the walls. Before this it could be useful to put up noggins to support the edges of your ceiling sheet material in between joists.
Walls, more VCL hanging down and overlapping the floor. Battens every 2'(or metric equivalent, 600mm?). 2" of celotex, It would be nice to line your windows with planed wood, so keep your tanalised battens 1/2" away from the window reveals and fasten the framing sideways to the battens. Again make provision for double width battens to hold the edges of your sheets. I wwould not use plasterboard for the walls unless you can protect it against knocks and its surface picks up grime.
Floor Two layers of DPC, to protect against pimples and sharp bits. 1" celotex with 22 mm P5 T&G. The eight of your kit will hold it in place. If you are installing proper machines (lathes/milling machines?), cut hole through T&G pull out the celotex and mount your kit on the DPC via another softish waterproof pad, Bit of lino/roofing felt?.
Its difficult to know where to draw the line, but I reckon loads of battens to help you put up shelving where you want. use bits of masking tape to mark out power points and switches so you can run in wiring/cut holes in your boarding at a convenient time.
As for your doors, big investment to replace or even to insulate. As they are for a car they could be just left fixed closed and insulated
and water sealed! Then a more convenient side door could be put in.. . . . Unless you want to get a 9' long lathe into the garage.
My thoughts
Frank

 

[Mattatooi]

Thank you very much Frank for your input.

Im not at home at the moment, but I think there is a gap on the underside around the garage facia for ventilation currently. Will check.

Just a quick questions, I presume I do not need to notify building control on this or do I? Its not going to be a "habitable" space. Its not an office or anything, but a workshop. And its no pro workshop. More of a hobby for myself!

Do I need to go with 100mm celotex for the roof? Could I get away with less? What about rockwool? Or is that a waste of time? There is no heating in the garage. I just want it to be damp free and draft free! Was considering just using a electric heater in the winter when its colder to get a bit of heat in the room. On the installation of it, I get all that. What happens around the edges where ceiling meets wall? Do I stop at the wall line and leave from top of wall to facia? As you can see I have a wooden beam on top of the bricks. I presume that is where I would stop? Also regarding the VCL. How does that work for lighting cables? Do I need to seal around where they poke through? What with? I was thinking even just using some thin hardboard for the walls and ceilings? Good or bad idea?

On the walls, how do you install celotex around socket cables? Do you just cut groove and a hole for them to pop through? I def will be adding sockets, as currently there is only 1 double socket and light in the lighting. Will be getting friend spark to do this for me.

With this method for walls you recommend I presume I would not be able to then just leave floor as and put SBR as you said above?

Lastly about the garage door. If I were to seal it, I presume this would not be usable. Is there anyway of making some sort of draft seal type thing around the door? And what about making a frame on the inside with celotex put on the inside of it? Or is that jus whacky? lol

Thanks again. I am just getting my head around this to work out if I can do it myself and get an idea of costings with materials. Prob might even get a builder round to give me a price aswell.

 

[theprinceofdarkness]

Roof insulation, yes you can use as much/little as you want Generally because hot air rises, the temperature at ceiling height will be greater then at floor level, so the heat losses would be greater. Use 3" Celotex?. Rockwool, you need twice the thickness for the same insulation value as Celotex. So you trade space for heat loss. 6" Rockwall on the ceiling would be a good compromise. Its a pain trying to get the Rockkwall to stay up between the joist before the boarding goes on. Its extremely floppy what you really want is a cheap net, held up with drawing pins (flat heads). I have used screws screwed into the sides of joists, right near their bottom with a diagonal wire that zig zags down the gap, works well but , boy is it labour intensive.
Building control don't need to know about this, unless you change the garage door(s), I doubt if they would be interested then.
Just run the all insulation right up to the ceiling, so there is not a gap where heat can "leak" out.
The electric cabling should be behind the Celotex and sockets cut it in, that why I used Rockwool, note about the floppyness
Yes the floor, You also need insulation over the floor, or your tootsies will freeze. I changed my mind about SBR because of the difficulty of sealing it to the wall VCl. Its about being pessimistic, you garage looks great at present, but once you cover up the inside of the wall, one can never be absolutely certain if any water is getting through the single skin wall until its too late. My present thought is that if a drip of water get through the walls, it will run down, being contained by the VCl. Now at floor level it will pool out over it. If the floor is covered with SBR the water will remain on top of it. Now with my DFA* the water will be under the DPC. This will mean your insulation and flooring will remain dry.
Frank
* DFA = Different Flipping Arrangement!

 

[Mattatooi]

Thanks Frank, been thinking about a few other problems.

So I do not have a gap around the facia board. Here is a pic of what there is (ignore obvious hole.. that will be filled);



Not quite sure how I am going to vent this. Do I need vent holes in between every joist on both sides? How big a hole? Also due to guttering, I would need to put holes at bottom, but isnt there a big risk to letting water in through this? The thing is, the wall that has the guttering is quite exposed and up a big hill and we get quite high winds with the classic sideways Irish rain quite common hah! So really dont know what to do here.

I was also thinking about ventilation in the garage once its all insulated. Currently there are two windows, but these do not open. My only way of letting air in would be through the door. Any thoughts on this? Should I bee looking at replacing one of the windows to allow it to open to allow some fresh air in without leaving the door open ? Or can I put in some kind of vent?

I can't quite get my head around how to seal off the main garage door, as this is currently the biggest source of drafts. Really don't know what I need to be buying / looking for to fit around it etc.

And lastly, the products them selves. I really have been googling all over the show and there just appears to be so many variations of these celotex boards. With other manufactures aswell. I really do not know what I should be aiming for. Even one brand has several types of 50mm boards, which to me appear to all look the same. What should I be looking at, and what should I be expecting to pay per sheet for 25mm,50mm and 100mm ?

Other than that I was designing rough stud plan in Sketch up to give me an estimate of material costs. Going around the pillars will be a pain, but I guess it would be worth it?

Thanks

 

[Mattatooi]

Oh and one other thing I forgot to ask. The VCL on the walls. At what point does t his go in. So in ceiling its between finish sheet material (plasterboard/osb etc) and the joists? You say then run this down the walls from ceiling. Are you saying this then goes up first in contact with wall, then stud/insulation? Or does it go in same place as ceiling? And following on from that, the DPM on the floor would run up the walls between wall and stud?

What sort of gauge am I looking for the VCL ? And similar for the DPM?

Cheers

 

[theprinceofdarkness]

Rain ingress through vent holes, I reckon that holes 1" diam should be enough, even though the building regs demand an enormous vent. I was thinking of some thing like these :- http://www.ebay.co.uk/itm/10-x-SKY-DISH-COAXIAL-CABLE-ENTRY-COVER-TV-AERIAL-WHITE-/251172187689 Just cut them down a bit so there is not such a big overlap at the top.I could not find out the size of them as ebay does not like me. The VCL I have used is a very thin green stuff, almost as thin as a free plastic bag from a supermarket. The screwfix stuff :- http://www.screwfix.com/p/vapour-barrier-green-300ga-2-5-x-20m/12869
If you start at the ceiling with a 6" hanging down the wall, then if the vertical plastic is fixed on the garage side then a drip will still be on the wall side. If the vertical plastic is tucked under the hanging bit then the drip will find its way out on to garage side of the vertical plastic.Likewise at the bottom, the wall plastic should overlap the floor by 6" with the heavy gauge DPC overlapping it and going up the wall 6" or so, still to contain the water on the outboard side.
Frank

 

[Mattatooi]

So just to clarify. From outside in.

For the ceiling; Roof etc, joists, with 50mm gap for ventilation at top, insulation inbetween joists. VCL over joists and insulation and finishing board on top.
For Walls, are you saying, drape the VCL from ceiling down 6", then put VCL on top of this hang and run down the wall. Batton stud on top of this, insulation inbetween etc and finish board on top.
For floor, DPM running up on top of the VCL from wall for 6".

I was only confused as I thought the vapour barrier should have gone on the "warmside", ie on top of inuslated studs on the walls?

Regarding ventilation holes, I was hoping to fit something a little more elegant. Having 15 of them fitted on the facia on both sides wouldn't be the prettiest. I can find plenty of round vents, such as 35mm hole, 50mm facing diameter, but none of them appear to be louvered. They are just a grill essentially. Such as https://www.sdslondon.co.uk/miscellaneous-vents/ventilation-trim-vent-37-mm.html or
https://www.sdslondon.co.uk/miscellaneous-vents/soffit-vent-50-mm.html . Any louvered type strips are a bit deep, such as https://www.sdslondon.co.uk/white-plastic-vents/louvre-165-x-75-mm.html -

I was hoping to just have a big long strip say 50mm in height with some louvres that I can just fit over all the holes and looks alot better. Kind of like a sofit fixing but louvered. Any ideas?

Thanks

 

[theprinceofdarkness]

With respect to your comments on the position of the VCL, you are correct. But that depends on the wall being of conventional construction with an outboard cavity. i.e. so the drips run down the cavity face of the wall. The insulation being kept dry by the cavity. So in modern brick wall, there is an outer skin, then a cavity pierced only by wall ties, then the foam, then the inner skin. In your case, as the inner wall is not free standing and held to the outer wall by ties, rather by battens the situation is a bit different. One way to copy normal construction closer, could be to have your battens on some form of vertical strip DPC, to isolate them from the possiblely damp wall, then leave a cavity before your insulation, then your VCL. this could work but it is fiddley, getting the DPC under the battens to have a little set on it so water will always run under the DPC, keeping the wood dry and the insulation clear of the cavity.
Just thought of a possible compromise, If you cut your VCL material into long strips and starting at the top, tape* a strip so it overlaps the hanging ceiling strip, repeat again, until the wall is covered with the VCL, but this time its got air vents in it pointing in the correct direction, so any intersticular condensation will run down it and drip outwards.
* tapes vertical, so horizontal joints in VCL are a little baggy, think tile hung buildings.
Frank

 

[theprinceofdarkness]

From you photograph I thought that the vent "outlet" would be behind the gutter, but I suppose on reflection that the face you see has not got the gutter on it. The vents you show are the ones I have seen before. If you Google "facia vents" then you get a lot of stuff that should have been built in! and they are black. The Soffit vent panels are very neat but are totally wrong for you as the is no water protection. You saying "strip", suppose you ran a length of electrical mini trunking along the facia, covering the holes, now if the back is drilled to match your holes (or bigger) and the underneath face was drilled every 1" with a 1/4 hole, that could look quite neat. Just the ends would need a bit of white plastic inserting and stuck with silicone just for appearance. I think you would have to make a jig to drill the small holes, else marking them out would be a trifle tedious. The stuff drills like butter, or even soft butter.
Frank

 

[Mattatooi]

Bringing this one back up. In the end I did nothing with the Garage, as when I started adding all the costs up it was just going to be too expensive for me at the time. So I put it all on hold. I am now looking at it more seriously though with a few adjustments.

Originally I had done this for a workshop; that is not really its primary purpose now. I want to use the space more as a gym space. It does not need to be perfect. So with that said, a few changes to original plans.

- Put up a stud wall infront of the large garage door (I never use and never will use it) - to stop all the draft and spiders getting in!
- Do not want to put a insulated floor in anymore. Instead I want to just put down some interlocking PVC tile stuff suitable for Gym use.
- Insulate ceiling and walls - but does not need to up to any spec
- Plasterboard roof and just white paint
- Undecided on wall finish - probably OSB painted white.
- Will use portable electric heater in the really cold days - however heating it is not as important, as It is being used as a gym. There is a washing machine and tumble dryer in garage currently, and when tumble dryer is on, it warms up the garage quite nicely.

With all that said, I want to check the order of build.

- Holes in fascia to allow airflow between joists
- Celotex or equiv in joists
- Where am I putting the VCL?
- How big a gap do I need for air flow. Joists height are 180mm/7"
- Celtox or equiv in walls
- Where does VCL go?
- With no floor insulation going in, how does this effect VCL and condesation etc?

If anyone can clarify order of things, be greatly appreciated. Sorry if it does not make any sense! Appears to be a lot of conflicting information out there about how to do single brick garage insulation.